In recent years, there has been a widely-used technology for obtaining white LEDs by arranging a fluorescent substance such as a YAG fluorescent substance around gallium nitride (GaN) blue light-emitting diode (LED) chips to mix blue light emitted from the GaN blue LED chips and yellow light emitted by secondary light emission from the fluorescent substance which has received the blue light.
As for such white LEDs, it is commonly performed to seal LED chips or their mounting areas with a transparent resin dispersing a fluorescent substance therein. However, since specific gravity of a fluorescent substance is larger than a transparent resin, a fluorescent substance settles before the resin hardens, which causes color unevenness in light emission.
Given the above, there have been proposed a variety of methods for suppressing settlement of a fluorescent substance to avoid color unevenness. For example, Patent Document 1 discloses that settlement or segregation of a fluorescent substance can be suppressed by using a silicone resin as a sealant, which resin has a viscosity of from 100 to 1000 cP when it hardens. Further, Patent Document 2 discloses a chip-part type LED configured such that LED elements are arranged between the upper end opening and the bottom end opening of a cylindrical container, the cylindrical container is filled with a translucent resin from the upper end opening to the bottom end opening, and the inner face of the container is formed so as to reflect light emitted from the LED element to the upper end opening.
Still further, Patent Document 3 discloses a light-emitting device composed of a liquid translucent sealant material and a lipophilic compound added thereto as an anti-settlement agent, which compound prepared by adding organic cations to a layered compound mainly composed of a clay mineral, and discloses a manufacturing method thereof.